Publications Details
An algorithm for using a slide-screw tuner as a computer-controlled impedance
In the testing of active microwave components, a common test procedure is to evaluate a device's performance when subjected to an all-phase, constant-standing-wave-ratio (APCS) load pull. Such a test specification is useful in verifying a device's stability and mismatch performance. Typically, APCS pulls are tediously performed by hand, with manually operated tuners. However, with the advent of mechanical, computer-controlled tuners, it is how possible to automate this procedure. At Sandia, the goal was to integrate an APCS pull capability into a multi-test, single-connection tester. (The single-connection concept implies that many test, such as network analysis, spectral analysis, and noise figure measurements can be made from a one-time, device-to-tester connection). Consequently, the slide-screw tuner was the obvious choice due to its removable probe capability. Hence, it became necessary to develop a custom algorithm capable of utilizing the tuner in an impedance-finding mode. The general concept used in implementing this capability was to empirically characterize the tuner over and acceptable range of tuner positions, and then use this characterization to intelligently predict the tuner positions needed to present the desired impedance. 4 figs.